Effect of posture on blood and intraocular pressures in multiple system atrophy, pure autonomic failure, and baroreflex failure.

BACKGROUND Intraocular pressure (IOP) may be partially under systemic vascular control. This study examined whether a correlation exists between blood and intraocular pressures in patients with autonomic dysfunction. METHODS AND RESULTS Eleven patients with 3 types of confirmed autonomic dysfunction (multiple system atrophy, pure autonomic failure, and baroreflex failure) were compared with age- and gender-matched controls and had IOP, systolic blood pressure, diastolic blood pressure, heart rates, and calculated mean arterial pressures (MAP) and mean ocular perfusion pressures (MOPP) measured in the supine, sitting, and standing positions. Data were analyzed with a general linear model repeated-measures ANOVA. All pressures for patients showed a dramatic decline (P<0.001) from supine to standing (MAP -31+/-14 mm Hg; IOP -6+/-3 mm Hg; MOPP -25+/-14 mm Hg) compared with controls (MAP +4+/-7 mm Hg; IOP -1+/-2 mm Hg; MOPP +6+/-7 mm Hg). There was no significant change in heart rate from supine to standing for patients compared with controls (P=0.648). Within both the multiple system atrophy (n=5) and pure autonomic failure (n=4) groups, all initial pressures were similar to control pressures in the supine position, whereas patients with baroreflex failure (n=2) had higher mean pressures than respective controls in the supine position. CONCLUSIONS In autonomic dysfunction, a large decrease in MAP correlated with a large decrease in IOP. These data suggest that the autonomic nervous system, perhaps through an influence on systemic blood pressure, has a significant role in IOP regulation.